a placozoan; the simplest known animal. Trichoplax adhaerens

Trichoplax adhaerens is a marine invertebrate distributed in tropical waters worldwide. It is the only member of the phylum Placozoa, and is thought to be the most anatomically simple multicellular animal. Its body is flat with no axis of symmetry, it possesses only four types of somatic cells and has one of the smallest known animal genomes. The phylogenetic position of Placozoa has not been determined.